摘要:

SummaryThe maximum likelihood, jackknife and bootstrap estimators of linkage disequilibrium, a measure of association in population genetics, are derived and compared. It is found that for point estimation, the resampling methods generate almost identical mean square errors. The maximum likelihood estimator could have bigger or smaller mean square errors depending on the parameters of the underlying population. However the bootstrap confidence interval is superior to the other two as the length of the intervals is shorter or the probability that the 95% confidence intervals include the true parameter is closer to 0.95. Although the standardised measure of linkage disequilibrium has a range from ‐1 to 1 regardless of marginal frequencies, it is shown that the distribution of this standardised measure is still not allele frequency independent under the multinomial sampling schem

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1991.tb00432.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary“So the last shall be first, and the first last; for many be called, but few chosen.”Matthew 20:16The “random” draw for positions on the Senate ballot papers in the 1975 election resulted in an apparently non‐random ordering, to the possible advantage of one particular party. This paper assesses the statistical significance of the 1975 draw and looks at possible causes of the evident non‐randomness. A simplified yet realistic mathematical model is used to describe conditions under which the so‐called donkey vote can have an effect on the final outcome of the election, thereby confirming the widely‐held belief that the order of parties on the Senate ballot paperisrelevant. We examine other Senate elections between 1949 and 1983 for the existence of relevant non‐randomness similar to the 1975 result. Finally, we report briefly on our submission to the 1983 Joint Select Committee on Electoral Reform, which led to an improvement in the random

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1991.tb00433.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryIn some vegetation types, total fuel loading (phytomass) can be predicted by easily‐measured variables such as vegetation type and height. A double sampling scheme is proposed in which fuel loading is estimated on a particular site by using quadrat sampling within patches of similar vegetation to develop a general prediction equation, and then line intercept sampling is used to estimate the mean of the easily‐measured variables on the site. This method is applied to estimate the total fine fuel loading on a heathland s

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1991.tb00434.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryConsider the model ofkpopulations whose densities are nonreg‐ular in the sense that they involve one or two unknown truncation parameters. In this paper a unified treatment of the problem of Bahadur efficiency of the likelihood ratio test for such a model is presented. The Bahadur efficiency of a certain test based on the union‐intersection principle is also studied. Some of these results are then extended to a larger class of nonregular densit

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1991.tb00435.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryCurrent methods for the design of efficient incomplete block experiments when the observations within a block are dependent usually involve computer searches of binary designs. These searches give little insight into the features that lead to efficiency, and can miss more efficient designs. This paper aims to develop some approximations which give some insight into the features of a design that lead to high efficiency under a generalized least‐squares analysis for a known dependence structure, and to show that non‐binary designs can be more efficient for some dependence structures. In particular, we show how neighbour balance and end plot balance are related to the design efficiency for low‐order autoregressions, and that under moderate positive dependence, replication at lag two can sometimes increase effic

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1991.tb00436.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryAn exact conditional test is developed for testing the absence of an edge in a graphical covariance selection model and is shown to be equivalent to a test based on the partial correlation coefficient. An example is given.

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1991.tb00437.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryConsider the linear regression modely=β01 +Xβ+ in the usual notation. It is argued that the class of ordinary ridge estimators obtained by shrinking the least squares estimator by the matrix(X1X + kI)‐1X'Xis sensitive to outliers in the ^variable. To overcome this problem, we propose a new class of ridge‐type M‐estimators, obtained by shrinking an M‐estimator (instead of the least squares estimator) by the same matrix. Since the optimal value of the ridge parameterkis unknown, we suggest a procedure for choosing it adaptively. In a reasonably large scale simulation study with a particular M‐estimator, we found that if the conditions are such that the M‐estimator is more efficient than the least squares estimator then the corresponding ridge‐type M‐estimator proposed here is better, in terms of a Mean Squared Error criteria, than the ordinary ridge estimator withkchosen suitably. An example illustrates that the estimators proposed here are less sensitive to outliers in the y‐variable than ordina

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1991.tb00438.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryA method of calculating simultaneous one‐sided confidence intervals for all ordered pairwise differences of the treatment effectsj–i, 1 i

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1991.tb00439.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryLet bekindependent populations having the same known quantile of orderp(0p1) and letF(x)=F(x/i) be the absolutely continuous cumulative distribution function of theith population indexed by the scale parameter1, i = 1,…, k. We propose subset selection procedures based on two‐sampleU‐statistics for selecting a subset ofkpopulations containing the one associated with the smallest scale parameter. These procedures are compared with the subset selection procedures based on two‐sample linear rank statistics given by Gill&Mehta (1989) in the sense of Pitman asymptotic relative efficiency, with interesting

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1991.tb00440.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryIn the planar regression model having two slope parameters and identically distributed errors, exact distribution‐free inference about one parameter may be carried out by grouping the observations, eliminating the nuisance parameter and reducing the model to simple linear regression, allowing exact distribution‐free methods for slope to be employed. This model reduction involves a loss of efficiency: the choice of an optimal grouping to minimize efficiency loss is discus

ISSN:0004-9581    

DOI:10.1111/j.1467-842X.1991.tb00441.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY